World’s largest heat pumps move toward scale in Europe

MVV Energie is moving ahead with what could become the world’s most powerful heat pump modules for district heating. In October, the parent company announced plans to install two units, each with a capacity of 82.5 megawatts, for a combined 162 megawatts. When fully online, the system could supply heat to about 40,000 homes via a linked district heating network. The Mannheim project will source heat from the River Rhine, drawing water through pipes that are 2 meters in diameter and capable of handling about 10,000 litres per second. The facility is planned for the site of a coal-fired plant that is being retired as part of cleaner energy ambitions. Construction is slated to begin next year, with the two-unit installation expected to be fully operational in the winter of 2028-29. A multi-step water-filtering system will prevent fish from being drawn in, and modelling suggests the project will raise the river’s average temperature by less than 0.1 degrees Celsius.

The scale of Mannheim’s plan reflects a broader push to deploy mega heat pumps to feed district heating networks as cities seek to decarbonize heat. Heat pumps transfer heat from air, water or ground sources into a usable heat stream for buildings; in these municipal-scale systems, the equipment operates far larger but uses the same physical principles as residential units. Industry officials stress that such projects rely on the availability of very large compressors and components often used in the oil and gas sector for storage or transport of fossil fuels. The Mannheim project underscores how transport logistics—whether by road or by river—shape the final footprint of giant units, with the Rhine location offering a straightforward electrical grid and an existing district heating loop that can absorb the new capacity.

The competition to secure megawatt-scale modules is evident beyond Germany as Everllence (formerly MAN Energy Solutions) pursues even larger goals. Everllence is advancing a 176-MW concept in Aalborg, Denmark, built from four 44-MW modules. While the Aalborg plan will rely on smaller, repeatable units, it represents the same shift toward modular megawatt-scale equipment designed to deliver heat across urban districts. In Aalborg and nearby Esbjerg, storage plays a key role: large hot-water tanks of about 200,000 cubic meters provide flexibility to shift heat production in response to price signals or renewables availability. The approach allows operators to pause heat pumps when electricity prices spike and instead draw heat from stored reserves. In this context, the price of heat-pump equipment itself has been cited at roughly €500,000 per megawatt of installed capacity, though this excludes buildings, enclosures and the associated infrastructure that must accompany a major installation.

Some projects are targeting the wind- and flood-prone, but water-rich contexts that help with heat extraction. Helsinki, Finland, illustrates a different path in which air-source or mixed approaches complement water sources. Helsinki’s Helen Oy has found that pulling large volumes of seawater directly would require an impractically long tunnel to reach sufficiently warm ocean water, even in a relatively mild climate. Instead, the city is pursuing a broader overhaul of its district heating network, which now spans about 1,400 kilometers and serves roughly 90% of buildings in the Finnish capital. The plan includes hundreds of megawatts of heat pumps, biomass burners and electric boilers to balance the system and absorb surplus renewable power. Electric boilers in particular are cheaper to install than large heat pumps and can quickly supply heat when renewables are abundant, helping to stabilize the grid while reducing dependence on fossil fuels.

A parallel track is being pursued in the United Kingdom, where new district heating networks are in development to serve universities and municipalities. The Exeter Energy Network is slated to deliver a minimum of 12 MW of heat to customers including the University of Exeter. Its backbone consists of three 4-MW air-to-water heat pumps, with the first unit expected to come online in 2028. In the broader policy and research community, experts emphasize that the UK has opportunities to expand district heating through use of waste heat, water in former mines and other thermal resources in post-industrial and rural areas that have space for heat storage and pumps. Keith Baker of Glasgow Caledonian University notes that such locations can serve as “sweet spots” for scaling up district heating beyond dense urban cores.

Across these developments, the overarching theme is clear: cities seeking decarbonization are increasingly turning to very large heat pumps as backbone assets for long-haul, low-emission heating. The newest mega projects combine water, air and biomass resources with regulated storage and grid-balancing capabilities to smooth demand and renewables variability. While capital costs remain high—Mannheim’s project is estimated at about €200 million and equipment costs alone can run into hundreds of millions for multi-megawatt installations—the potential to replace aging coal-fired or oil-based heat sources with scalable, flexible heat pumps is drawing interest from utilities, city planners and engineers around the world. The growing array of projects also highlights the need for careful environmental safeguards, including fish protection, river temperature modeling and careful siting to minimize ecological impact while maximizing decarbonization benefits.

As nations push to meet climate targets, the deployment of mega heat pumps within district heating networks is poised to accelerate. The Mannheim and Aalborg projects illustrate a shift toward modular, scalable solutions that can be rolled into existing infrastructure, while Helsinki and Exeter show how European cities are weaving heat pumps into broader energy systems that include electric boilers, biomass, storage and demand response. The sector’s trajectory will depend on continued advances in compressor technology, advances in heat storage, and policy and market frameworks that encourage investment in long-lived, low-emission heat assets. The combination of large-scale heat pumps, robust district heating networks and effective storage could become the backbone of urban heating in the coming decade, supporting decarbonization goals while maintaining reliability and cost-competitiveness for residents and businesses.